A hon-shimeji mushroom is a mushroom, which generates on the ground surface in a forest of quercus serrata grove or a mixed forest of quercus serrata and red pine around in the middle of October. As people say “a hon-shimeji mushroom is excellent in taste, while a matsutake mushroom is excellent in flavor”, a hon-shimeji mushroom as well as a matsutake mushroom are recognized as the highest grade edible mushrooms in Japan. Recently, for edible mushrooms including an enokitake mushroom (Flammulina velutipes), a hiratake mushroom (Pleurotus ostreatus), a nameko mushroom (Pholiota nameko), a bunashimeji mushroom (Hypsizigus marmoreus, Lyophyllum ulmarium), a maitake mushroom (Grifola frondosa) and the like, a fungal bed cultivation method has been established, wherein a mushroom is artificially cultivated by using a culture medium containing mixed nutrient sources of sawdust, rice bran, wheat bran and the like. Thus, these mushrooms can be harvested stably in any season throughout the year. Although it has also been desired to establish an artificial cultivation method of a hon-shimeji mushroom because of its excellent taste, an artificial fungal bed cultivation thereof has been considered to be difficult because a hon-shimeji mushroom is a mycorrhizal fungus, while the above mentioned enokitake mushroom and the like are wood-rotting fungi.
Ohta of Shiga Prefectural Forest Research Center succeeded in a fungal bed cultivation of a hon-shimeji mushroom for the first time. Patent Document 1 discloses a fungal bed cultivation method of a hon-shimeji mushroom using wheat and the like, and non-Patent Document 1 discloses an experiment for generating fruit body of a hon-shimeji mushroom using a culture medium containing wheat and the like.
In addition, Patent Document 2 discloses a method for incubating the mycelia of a mycorrhizal fungus using a culture medium in which peat moss is used as a base material and starch and the like are added thereto and, in non-Patent Document 2, the inventors of the above patent document report an experiment for generating fruit body of a hon-shimeji mushroom using a culture medium in which peat moss is used as a base material, and starch and the like are added thereto.
However, the method described in Patent Document 1 requires much cost for a culture medium because wheat, and the like used in the culture medium are expensive. Further, the method described in Patent Document 2 does not reach a commercial production level due to a low yield of a fruit body.
Recently, various cultivation methods of a hon-shimeji mushroom have been disclosed for the commercial production of a hon-shimeji mushroom. Patent Document 3 discloses a culture medium for fungal bed cultivation of a hon-shimeji mushroom which comprises Panicoideae plant, and a method for cultivating a hon-shimeji mushroom using the culture medium. Further, Patent Document 4 discloses a fungal bed cultivation method of a hon-shimeji mushroom which comprises preparing a mixed culture medium containing at least corn powder and sawdust of broad leaf tree, inoculating the mycelia of a hon-shimeji mushroom on the mixed culture medium in a moisturized wet state, and incubating the culture medium at a temperature of 30° C. or lower to generate a fruit body.
Patent Document 5 discloses a fungal bed cultivation method of a hon-shimeji mushroom which comprises adding crushed oyster shell to a culture medium on which the mycelia of a hon-shimeji mushroom have been inoculated so that a fruit body can generate by incubating, them in a moisturized wet state, and adjusting pH of the culture medium to a range below 7.
Patent Document 6 discloses a fungal bed cultivation method of a hon-shimeji mushroom which comprises using a mixed culture medium prepared by adding small amounts of wheat and/or rice to a culture medium containing corn and sawdust and mixing them, inoculating the mycelia of hon-shimeji mushroom on the culture medium in a moisturized wet state, and incubating it to generate a fruit body.
The Example of Patent Document 1 investigates whether or not a hon-shimeji mushroom strain forms primordia of a fruit body when the mycelia are incubated at 23° C. for 70 days, followed by lowering the temperature to 15° C. And, a formation ratio of a fruit body has been increased by covering the surface of the culture medium with peat. Further, in non-Patent Document 1, the surface of a culture medium is covered with peat with a thickness of 1 cm, when the mycelia of a hon-shimeji mushroom are extended in an incubation step at 22° C. Then, the culture medium is further incubated for additional two weeks and, after completion of incubation, the culture medium is transferred to a generation room at 15° C. to generate a fruit body.                In non-Patent Document 2, formation of primordia of a fruit body is recognized on the 13th to 15th day after incubation of a hon-shimeji mushroom strain by inoculating the mycelia of the strain on a culture medium, incubating and maturing it at 23° C., and then carrying out a generation operation in a generation room at 16° C.        Patent Document 3 discloses a bottle cultivation method which comprises steps of preparation of a culture medium, filling of a bottle, sterilization of the culture medium, inoculation, incubation (culture), sprouting, growth (cultivation), and harvesting, wherein primordia of a fruit body is formed in the step of sprouting after incubation. Further, in Example thereof, the sprouting is carried out with a cover of Akadama soil.        In Example of Patent Document 4, generation of a fruit body of a hon-shimeji mushroom strain is promoted by incubating the strain at 23° C. for 60 days, incubating the mycelia for additional 7 days with covering the surface of a culture medium with Kanuma soil, transferring the culture medium to a generation room at 15° C.        In Example of Patent Document 5, the mycelia of hon-shimeji mushroom strain is incubated at 23° C. for 70 days, the culture medium is transferred to a generation room at 15° C., and the cap is removed when a small fruit body is appeared, then the fruit bodies are harvested when pilei have grown to open.        In Example of Patent Document 6, the mycelia of hon-shimeji mushroom strain is incubated at 23° C. for 55 days, further incubated for additional 10 days with covering the surface of the culture medium with Kanuma soil, and the culture medium is transferred to a generation room at 15° C. to promote generation of a fruit body.        
Patent Document 1: JP 7-115844 A
Patent Document 2: JP 6-153695 A
Patent Document 3: JP 2000-106752 A
Patent Document 4: JP 2002-247917 A
Patent Document 5: JP 2005-27585 A
Patent Document 6: JP 2007-54044 A
Non-patent Document 1: “Nihon-Kingakkai Kaihou” (Journal of the Mycological Society of Japan), volume 39, pages 13-20, 1998
Non-patent Document 2: “Nihon-Kingakkai Kaihou” (Journal of the Mycological Society of Japan), volume 35, pages 192-195, 1994